This invention relates generally to diode laser control and more particularly to the suppression or altering system kink response of occurring in the output of multiple laser diodes.
Laser diode kinking along the L-I characteristic curve for a laser diode generally results in a sign change in the slope efficiency, dL/dI. Kinking inverts the phase of the feedback employed in laser diode systems utilizing closed loop control with a detection system for the output power to provide a feedback signal to change the drive current to the laser diode. When the sign of the slope efficiency changes relative to the output power, there results power instability and laser control problems. Problems in control of kinking can be solved by employing sophisticated digital methods to overcome a particular dL/dI anomaly in the system. However, a simpler solution, compared to such a more expensive approach, is more desirable for commercial applications in the control of laser diode systems.
Thus, it is a primary object of this invention to suppress L-I kinking in the output of a laser diode source or sources and its negative effect in feedback control of laser diode current operation.
According to this invention, in one approach, multiple laser diode output are combined so that the negative value effects of current change due to L-I kinking are suppressed. In an alternate approach, a high frequency dither is imparted on the pump current supplied to the laser diodes and its applied frequency is limited in effective bandwidth of the detection system to less than the dither frequency. A further and more successful approach is the combination of these two foregoing approaches.
Other objects and attainments together with a fuller understanding of the invention will become apparent and appreciated by referring to the following description and claims taken in conjunction with the accompanying drawings.